High-temperature corrosion behavior of iron-aluminide alloys and coatings

An Fe-28 at.% Al-2% Cr alloy doped with Y{sub 2}O{sub 3} showed improved scale adhesion relative to a dispersion-free form of the same composition. However, doping with CeO{sub 2} or La{sub 2}O{sub 3} was detrimental to oxidation behavior. A study of weld-overlay iron-aluminide coatings showed that, those with sufficiently high aluminum concentrations had sulfidation resistance in H{sub 2}S-H{sub 2}-H{sub 2}O-Ar at 800 C equivalent to the most resistant bulk iron aluminides. These corrosion-resistant coatings have the potential to be effective barriers in high-temperature sulfidizing environments provided the appropriate combinations of filler metal, process parameters, and substrate are used to produce adequate aluminum concentrations and minimal chromium contents. Exposures in an oxidizing/sulfidizing environment containing varying amounts of HCI at 450 and 550 C showed that Fe{sub 3}Al alloys had good corrosion resistance